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Full text of "The manufacture and properties of iron and steel"

METHODS  OF MANUFACTURE.
231
silicon in the pig-iron, which will amount to 5 per cent, of the total. In the practical conduct of a steel plant these data are not necessary, but they become of value in the discussion of different methods. Thus Mr. Talbot refers to the gain in his process, and the fact may escape notice that a large part of the oxide additions is scale containing 74.5 per cent, of metallic iron. In the case of a 50-ton charge using 12 tons of ordinary ore, carrying 62 per cent, of iron, in the wet state, the metallic iron in' this addition will be 7.44 tons. If the same quantity of rich scale be used, the amount of iron will be 8.94 tons, a difference of 1.50 tons of metallic iron in a charge of 50 tons, or 3 per cent, of the weight of ingots. Thus the use of rich scale instead of rich ore means a gain of 3 per cent, in the ingots, and there is no glory to be given to the process on account of it because it is inevitable. Scale was used to bring down a bath of pig-iron long before an open-hearth furnace was built. It has less oxidizing power per unit of iron than hematite ore, so that it is possible to use more than would be used of rich ore and the extra iron is clear gain.
SEC. Xllh.—The duplex process.—The use of all pig-iron in a stationary basic open-hearth furnace is not altogether advantageous, and it is an easy and attractive solution of-the problem to first de-siliconize and partially decarburize in a Bessemer converter, either acid or basic, and then finish in an open-hearth furnace, either acid or basic. At one works in Europe this practice has been carried on for some years, and the operation is an easy way of making steel from phosphoric pig-iron. I believe it is an expensive way, for more than one reason. In the acid converter, the loss will be very nearly as much as in the making of steel. The silicon will be entirely oxidized and the full quantity of slag formed. The slag will be somewhat more viscous if the charge is not entirely decar-burized, but under these conditions the amount of shot will be more than when the slag is liquid. The total loss of iron, chemically combined and mechanically held, will be constant, whether the slag be viscous or liquid. The carbon must be reduced to about one per cent, if the open-hearth furnace is to do its work in quick time, and we have the following result:
Loss in the converter: